JP4161833B2 - Wiper motor mounting structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wiper motor mounting structure for driving a rear wiper mounted at the rear of a vehicle.
[0002]
[Prior art]
In general, various noises are generated inside and outside the passenger compartment when an automobile is running. As one of such noises, so-called low-frequency booming noise is widely known. This low-frequency booming noise is generated when the system consisting of tires and suspension components resonates due to input from the road surface, and the amplified vibration is transmitted to the vehicle interior via the vehicle body panel. Resonance in the acoustic system of the interior space (the interior space of the vehicle acts as a resonance space) and the resonance of the structural system such as the door panel are noises that are excited. Note that the low-frequency booming noise mainly occurs around 40 Hz and around 80 Hz of its overtone.
[0003]
Such low-frequency booming noise is unpleasant noise that presses the passenger's ears, and there is a demand for reducing such noise as much as possible.
On the other hand, in order to reduce such low-frequency noise, it is known that the resonance frequency f1 of the acoustic system and the resonance frequency f2 of the structural system may be shifted from the natural frequency of the system composed of tires and suspension parts. It has been.
[0004]
However, among these, the resonance frequency f1 of the acoustic system is mainly determined by the vehicle interior length and volume, and the resonance frequency f2 of the structural system is determined by the shape and mass of the door panel. Is not something that can be changed easily. In addition, the natural frequency of the system composed of tires and suspension parts is determined by the characteristics of the tires and suspensions, and these values cannot be easily changed. The resonance frequency f1 and the resonance frequency f2 are set to the suspension. It is difficult to reduce low-frequency booming noise by shifting from the natural frequency of the system.
[0005]
On the other hand, for example, in Patent Document 1 below, a dynamic damper is provided at a position symmetrical to the rear wiper of the back door of the vehicle body to suppress the vibration of the back door and suppress the generation of noise due to the vibration of the back door. The technique made to do is disclosed. Patent Document 2 discloses a technique related to a vibration isolating mount for a motor that increases the mounting rigidity with respect to the vehicle body.
[0006]
[Patent Document 1]
Registered Utility Model No. 2536208 [Patent Document 2]
Japanese Patent Laid-Open No. 2000-81089
[Problems to be solved by the invention]
However, in the technique of Patent Document 1, it is possible to shift the resonance frequency f2 of the structural system from the frequency of the low frequency booming noise by providing a dynamic damper on the back door, but the weight of the back door increases accordingly. As a result, there is a problem that the weight of the vehicle is increased, and there is a problem that the cost is increased.
[0008]
Moreover, the technique of patent document 2 is only a technique of improving the attachment rigidity of the vibration-proof mount and increasing the attachment rigidity, and cannot reduce the low-frequency booming noise.
The present invention was devised in view of such problems, and an object of the present invention is to provide a wiper motor mounting structure that can reduce low-frequency muffled noise in a vehicle without incurring an increase in cost or weight. To do.
[0009]
[Means for Solving the Problems]
For this reason, the wiper motor mounting structure according to the first aspect of the present invention is a wiper motor mounting structure for driving a wiper mounted on a rear gate at the rear of the vehicle, and the wiper motor is attached to the rear gate via a rubber bush. The natural frequency of the wiper motor including the rubber bushing is the resonance frequency of the acoustic system in the interior space of the vehicle so that the wiper motor functions as a dynamic vibration absorber that is mounted and reduces low-frequency noise generated in the vehicle interior. The hardness of the rubber bush is set to be equal to.
[0010]
According to such a configuration, since the wiper motor attached to the rear gate functions as a dynamic vibration absorber (dynamic damper), it is possible to reduce low-frequency booming noise in the passenger compartment .
[0011]
The effect is particularly great when the rear gate is configured to open and close in the vertical direction such as having a hinge mechanism above and a latch mechanism below.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a wiper motor mounting structure according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic perspective view of a vehicle to which the present invention is applied.
A vehicle 1 shown in FIG. 1 is a so-called wagon type vehicle, and includes a back door (rear gate) 2 behind the vehicle body. The back door 2 has a hinge mechanism on the upper side and a latch mechanism (both not shown) on the lower side, and the rear gate 2 opens and closes in the vertical direction with the hinge mechanism as a fulcrum.
[0013]
The back door 2 is provided with a rear wiper mechanism 3 for wiping the glass 2a. The rear wiper mechanism 3 is mainly interposed between a wiper main body (wiper) 4, a wiper motor 5 (see FIG. 2) for driving the wiper, and the wiper motor 5 and the wiper main body 4 to drive the wiper motor 5. A link mechanism (not shown) for transmitting force to the wiper body 4 is provided.
[0014]
The wiper motor 5 is attached to the back door 2 via a rubber bush 51 and a bracket 52 shown in FIG. Specifically, a weld nut (not shown) is welded to the vehicle body side, that is, the door panel of the back door 2, and a bolt (not shown) is screwed to the weld nut via a rubber bush 51 and a bracket 52. Thus, the wiper motor 5 is elastically supported by the back door 2. In FIG. 2, reference numeral 53 denotes a gear that transmits driving force from the motor 5, and reference numeral 54 denotes a rotating shaft that meshes with the gear 53 and is connected to the above-described link mechanism.
[0015]
By the way, the rubber bushing 51 that elastically supports the wiper motor 5 is conventionally provided for the purpose of preventing the occurrence of abnormal noise by avoiding contact between metals of the door panel and the bracket. There were no specially required specifications.
On the other hand, in the present embodiment, the hardness (or spring constant) of the rubber bush 51 is set so that the wiper motor 5 functions as a dynamic damper that reduces low-frequency booming noise. Specifically, the hardness of the rubber bush 51 is set so that the natural frequency of the wiper motor assembly including the rubber bush 51 and the bracket 52 substantially matches the resonance frequency (about 40 Hz) of the acoustic system in the vehicle interior space. Has been. In the following description, the wiper motor 5 refers to a wiper motor assembly including a rubber bush 51 and a bracket 52 unless otherwise specified.
[0016]
Here, as described above, a low-frequency booming noise is generated as one of the noises in the passenger compartment when the automobile is running. This low-frequency muffled sound is excited by a combination of resonance in the acoustic system of the vehicle interior space and the resonance of the structural system such as the door panel, which are input from tires and suspension parts. appear.
In order to reduce such low-frequency muffled sound, the resonance frequency f1 of the acoustic system or the resonance frequency f2 of the structural system may be shifted from the above-mentioned low-frequency muffled sound frequency (about 40 Hz). The frequency f1 and the resonance frequency f2 of the structural system are basically unique values determined by vehicle specifications and are difficult to change.
[0017]
Therefore, as described above, in the present embodiment, the hardness of the rubber bush 51 is set so that the natural frequency of the wiper motor 5 substantially matches the resonance frequency of the acoustic system in the vehicle interior space, that is, the frequency of the low-frequency booming noise. It is set. And by setting in this way, the wiper motor 5 functions as a dynamic damper (dynamic vibration absorber), so that the vibration of the back door 2 is suppressed, and as a result, low-frequency booming noise can be reduced.
[0018]
Hereinafter, the hardness of the rubber bush 51, that is, briefly described method of setting the spring constant K, the natural frequency f _m of the motor 5 can be represented by the following formula (1) the mass of the motor 5 and M.
f _m = (1 / 2π) · (K / M) ^1/2 (1)
Therefore, it is possible to easily set the spring constant K of the rubber bushing 51 by substituting the values of the frequencies of the target to f _m of formula (1).
[0019]
Since the wiper motor mounting structure according to an embodiment of the present invention is configured as described above, the wiper motor 5 functions as a dynamic damper, and low-frequency booming noise is reduced. Hereinafter, the operation will be specifically described with reference to FIG.
In FIG. 3, the horizontal axis represents frequency [Hz] and the vertical axis represents acoustic sensitivity [dB / N]. The acoustic sensitivity is an index representing the ease of sound transmission, and corresponds to the loudness of the sound. In the present embodiment, the acoustic sensitivity is obtained by a numerical experiment using a model of the value at the front seat when the back door 2 is vibrated.
[0020]
A line a in the figure indicates characteristics when the wiper motor 5 is attached to the back door 2 without elastic support, that is, when the wiper motor 5 without using the rubber bush 51 is attached to the back door 2. In this case, the wiper motor 5 and the back door 2 can be regarded as an integral structure. In this case, as shown in the figure, noise peaks occur at two locations of about 42 Hz and about 54 Hz.
[0021]
A line b indicates characteristics when the hardness of the rubber bush 51 is set so that the natural frequency of the wiper motor 5 matches the natural frequency of the back door 2. In this case, noise peaks occur at three locations of about 42 Hz, about 47 Hz, and about 63 Hz, and in the vicinity of 54 Hz between the second peak (about 47 Hz) and the third peak (about 63 Hz). The acoustic sensitivity is greatly reduced. However, what the passenger feels as a low-frequency booming sound is the frequency from the first peak (about 42 Hz) to the second peak (about 47 Hz), and in this frequency range, the acoustic sensitivity increases compared to the characteristics of line a. The noise cannot be reduced.
[0022]
It was experimentally confirmed that when the wiper motor 5 is elastically supported except for the case of the characteristic of the line c described later, three peaks appear as shown by the line b. Further, when the wiper motor 5 is attached to the back door 2 without elastic support as shown by the line a, or when the wiper motor 5 is not attached, that is, when the back door 2 can be regarded as an integral structure. It was confirmed that two peaks appeared.
[0023]
On the other hand, the line c shows the characteristic when the hardness of the rubber bush 51 is set so that the natural frequency of the wiper motor 5 matches the resonance frequency of the acoustic system. In this case, there are two noise peaks of about 39 Hz and about 57 Hz, and it can be seen that even when the wiper motor 5 is elastically supported, the peaks appear exceptionally only at two places. Further, since the wiper motor 5 functions as a dynamic damper, the vibration of the back door 2 is suppressed, and the overall acoustic sensitivity is lower than the characteristics of the lines a and b. Sound can be reduced. Although FIG. 3 shows the characteristics of acoustic sensitivity at the driver's seat, the acoustic sensitivity decreases at any position in the passenger compartment.
[0024]
As described above, according to the wiper motor mounting structure according to the present embodiment, the hardness of the rubber bush 51 is set so that the natural frequency of the wiper motor 5 is equal to the resonance frequency of the acoustic system in the interior space of the vehicle 1. With a simple configuration, there is an advantage that low-frequency muffled noise in the passenger compartment can be reduced without causing an increase in cost or weight.
[0025]
In addition, this invention is not limited to the above-mentioned embodiment, A various deformation | transformation is possible in the range which does not deviate from the meaning of this invention. For example, in the above-described embodiment, the back door is provided with a hinge mechanism on the upper side and a latch mechanism on the lower side, and is configured to open and close in the vertical direction with the hinge mechanism as a fulcrum. The mechanism and the opening / closing direction are not limited to those described above, and are configured to open in the left-right direction, or the door is divided vertically so that the upper half opens upward and the lower half opens downward. It can also be applied to things. However, as in this embodiment, the back door with a structure that opens and closes in the vertical direction using the upper hinge mechanism as a fulcrum has lower mounting rigidity and is more likely to resonate. large.
[0026]
Further, other detailed configurations can be appropriately changed as necessary.
[0027]
【The invention's effect】
As described above in detail, according to the wiper motor mounting structure of the present invention, the wiper motor attached to the rear gate functions as a dynamic vibration absorber (dynamic damper). There is an advantage that can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of a vehicle to which a wiper motor mounting structure according to an embodiment of the present invention is applied.
FIG. 2 is a schematic diagram for explaining a wiper motor mounting structure according to an embodiment of the present invention.
FIG. 3 is a view for explaining the operation of the wiper motor mounting structure according to the embodiment of the present invention.
[Explanation of symbols]
1 Vehicle 2 Rear gate (back door)
3 Rear wiper mechanism 4 Wiper (wiper body)
5 Wiper motor (motor)
51 Rubber bush

Claims (2)

A wiper motor mounting structure for driving a wiper mounted on a rear gate of a vehicle,
The wiper motor is attached to the rear gate via a rubber bush,
The natural frequency of the wiper motor including the rubber bush is equal to the resonance frequency of the acoustic system in the interior of the vehicle so that the wiper motor functions as a dynamic vibration absorber that reduces low-frequency noise generated in the vehicle interior. A wiper motor mounting structure, characterized in that the hardness of the rubber bush is set. The rear gate, characterized in that it has a latching mechanism downwardly provided with a hinge mechanism upwardly, the mounting structure of the wiper motor according to claim 1, wherein.

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